Better Crystals for Crystal Analysis G e t t i n g g d crystals is oRen a problem for scientists, laboratory workers, and students. One problem is caused when same crystals are air-sensitive, even though their compounds are not. Due to the Lewis acid nature of the metals, their rrystals are shattered by either the rapid removal of solvent or contact with air. Repeated analyses have shown that there is no chance - in the chemical composition of these compounds; the only source of the problem is their sensitivity toward air. These compounds donot give g d crystals at low temperature or they take a long time for crystal formation. We have develoaed an easv and relatively. raaid . method of cwstallization by slow evaporation under an inert atmosphere. The air-sensitive compound is placed in a Schlenk tube and crystallization solvent, either single or mixed, is added. The tube is then closed with a rubber stopper and sealed with paralilm. The arm of the Schlenk tube is connected to argon or nitrogen, which leads to very slow evaporation. The vapors of the solvent can be allowed to escape about three times a week by careful release of the argon or nitrogen tube. This method will give good crystals in about two weeks. Saqib Ali, M. Danish, and M. Mazhar Quaid-i-Azam University Islamabad. Pakistan
Volume 72 Number 1 January 1995
61
